1. Field of the Disclosure
The present disclosure relates to a substrate for growing a semiconductor device, and more particularly, to a Pendeo-epitaxy growth substrate on which a solution blocking layer for preventing a flow of solution that may cause contamination of a semiconductor device during a manufacturing process of the semiconductor device is formed, and a method of manufacturing the same.
2. Description of the Related Art
Semiconductor devices, e.g., nitride semiconductor laser diodes, are manufactured by forming nitride semiconductor layers on sapphire (Al2O3) substrates. Sapphire substrates utilize a simple preprocessing process and are stable at high temperatures at which nitride semiconductor layers are formed. However, since sapphire substrates and nitride semiconductor layers have differences with respect to a lattice constant and a coefficient of expansion, sapphire substrates may have a crystal defect and may be easily deformed. GaN substrates having a low defect density are manufactured by forming thick GaN layers on sapphire substrates using hydride vapor phase epitaxy (HVPE). However, the HVPE lacks reliability in terms of defect density and size. To replace the HVPE, eptitaxial lateral overgrowth (ELOG) and Pendeo are proposed to reduce the defect density by using lateral growth. A Pendeo-epitaxy growth process is disclosed in U.S. Pat. No. 6,521,514.
FIGS. 1A through 1C are cross-sectional views of a Pendeo-epitaxy growth substrate while undergoing a conventional process of formation. The process involves forming a GaN substrate using Pendeo-epitaxy growth.
Referring to FIG. 1A, a substrate 10 is coated with nitride and is partially etched to form an etching area 11 that exposes a portion of the facet of the substrate 10 and a pattern area 12.
Referring to FIG. 1B, if the nitride is laterally grown from the pattern area 12, growth areas 13 are grown laterally outward from the pattern area 12.
Referring to FIG. 1C, if the growth areas 13 keep growing, all the growth areas 13 are combined to complete a nitride layer. As a result, a crystal defect primarily occurs in the pattern area 12, and the growth areas 13 have a very low defect density. However, air gaps 14 generated at the bottom of the growth areas 13 are movement paths for various kinds of solutions during the manufacturing process of the substrate 10. Such solutions are combined with Ga melt to form a mixture. The mixture is physically splashed during the manufacturing process of a semiconductor device (e.g., during cleaving), which causes a phenomenon as illustrated in FIG. 20. If the mixture adheres to the entire facet of the substrate 10, the substrate 10 cannot properly send an electric current but instead another path sends the electric current, which greatly reduces the yield of the semiconductor device manufacture.
FIG. 2A is a diagram of a wafer used in a conventional Pendeo-epitaxy forming process. Referring to FIG. 2A, all the areas of a substrate 20 are not used except for a usable area 21 which is inside the substrate 20. In an expanded boundary A of the usable area 21, pattern areas 23 and an etching area 24 are formed on the substrate 20. The pattern areas 23 are divided into usable areas A1 and unusable areas A2 after the semiconductor device is manufactured. The etching area 24 is removed from areas between the usable areas A1 and the unusable areas A2 in order to prevent a crack from occurring during a laser diode (LD) structure growth process.
FIGS. 2B and 2C are cross-sectional images of a conventional semiconductor device after the semiconductor device is grown by a Pendeo-epitaxy process. Referring to FIGS. 2B and 2C, after the semiconductor device is formed on the substrate formed using the Pendeo-epitaxy process, large contamination areas 14a are generated in air gap areas of the substrate due to contamination of solution during the manufacturing process of the semiconductor device. The contamination areas 14a are frequently generated due to a solution being splashed during a cleaving process after forming growth areas 13 on the substrate and after forming a semiconductor layer 15 at the top of the growth areas 13. As described above, since the air gaps are indispensable to the Pendeo-epitaxy growth process, a method of preventing contamination of the air gaps and a yield reduction is required.